[FloppyPlops]

stand alone tablets are not intersting to hack

So hacking in your mind is like in CSI, where some bad actor is really invested in hacking your specific tablet?
It's a numbers game. Once W10 goes out of support, hackers will be massively invested in discovering and exploiting vunerabilities in it, because they know there will be hundreds of thousands of users still using it. They don't target invividual machines, they cast a net and see what it catches. And it might be ransomware, to steal your data, or to spy on you through your webcam, it might be to set up your tablet as part of a botnet - which you never even notice happen, or something else currently unimaginable.

For W10 users, yes, there are technically ways around the issue: Buy new hardware, cut yourself off from the internet, don't use your tablet for anything else. Great (if inconvenient) for those who can afford separate hardware for every activity in their lives.
But it sounds like you're still expecting the developer of MS to keep developing their software for an unsupported operating system. Which might mean no extra overhead to start with, but what happens when the tools and frameworks (created by Microsoft or third parties) that they require to develop MS gradually drop support for W10 too?